Cancer is the name given to a group of more than 100 diseases that have, in common, the disorganized growth of cells that invade tissues and organs, and which may spread to other regions of the body, in what is called metastasis.
Different types of cancer correspond to various cell types of the body. For example, there are several types of skin cancers, since the skin comprises more than one cell type. If the cancer starts in epithelial tissues, such as skin or mucosa, it is called carcinoma. If it starts in connective tissues, such as bones, muscles or cartilage, it is called sarcoma. Other characteristics that differentiate one type of cancer from others are the speed of cell multiplication and their ability to invade tissues and organs, in the vicinity or distantly from its origin.
The difficulty for the effective treatment of cancer relates to establishing the distinction between malignant and normal cells of the body. Both are derived from the same source and are very similar, and for this reason, there is no significant recognition by the immune system as to the threat. Until now, cancer can be treated by surgery, chemotherapy, radiotherapy and immunotherapy (monoclonal antibody therapy). The choice of treatment depends on the location, tumor grade and stage of the disease, as well as the general condition of the patient. The complete removal of the tumor without damage to the rest of the organism is the main goal of the treatment. Sometimes, this can be achieved through surgery, but the propensity of the disease to invade adjacent tissues or to spread to distant sites (metastasis) often limits its effectiveness. The chemotherapy effectiveness is, in most cases, limited by its toxicity to other tissues (cells) of the organism, as well as radiotherapy, which can also damage normal tissues. In immunotherapy, carcinogenic cells developed mechanisms to escape from the immune response, a phenomenon known as resistance to treatment.